This invention generally concerns a mechanically-adjustable variable speed drive, and in particular the improved combination of a dry traction type mechanical variable speed drive apparatus with electric remote control for actuating same.
A number of commercial devices and processes require variable speed power inputs, while constant speed electric motors are generally cheaper and more rugged and reliable than variable speed electric motors. Mechanically-adjustable variable speed drives are known for coupling between constant speed motors and devices requiring variable speed power inputs. In effect, the variable speed drive is used to change the output speed of the electric motor as needed for the device being driven. In actuality, mechanical linkages of the drive apparatus are altered so that the output speed of the variable speed drive is controllably varied relative the constant speed input thereof.
One example of a mechanical adjustable speed drive is the DISCTRAC dry traction, disc-type drive distributed by the present assignee. In general summary, such adjustable speed drive has a housing with co-axially aligned input and output, and uses a dual pair of friction discs/rings. A first friction disc and friction ring are associated with the input and output, respectively. Another respective friction ring and friction disc are carried on opposing ends of a movable centerpiece element and associated at slight angles with the input friction disc and output friction ring, respectively. A handwheel may be used to manually rotate a shifting screw threadably engaging the centerpiece element so as to shift its friction disc and ring relative the co-axially aligned input and output. The radii of respective contact areas between the disc/ring pairs is thereby altered, which results in speed variation of the drive output relative the input thereof.
In another embodiment of such DISCTRAC apparatus, the handwheel (mechanical variator) is replaced with a bi-directional electric motor (electrical variator) coupled by a right-angle worm gear drive arrangement to the shifting screw. The motor controllably rotates the shifting screw to in turn adjust the output speed of the drive apparatus relative the input thereof.
Furthermore, alternative basic configurations of dry traction, disc-type devices are known. For example, a configuration using a single pair of friction disc and ring generally replaces the abovementioned sliding centerpiece element and its ring/disc pair with a controllably positioned drive motor which is also shifted relative the housing drive train for the purpose of varying output speed versus input speed, as understood by those of ordinary skill in the art. Such drive motor may be physically shifted with mechanical (e.g. handwheel) actuation or a right-angle worm gear electric motor arrangement, similar to the "electric" DISCTRAC embodiment. Present reference throughout to a dry traction disc-type mechanical adjustable speed drive apparatus is generally intended to refer to any and all modifications and variations of such basic apparatus.